/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.core;



import com.bff.gaia.unified.sdk.transforms.windowing.BoundedWindow;

import com.bff.gaia.unified.sdk.values.PCollectionView;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.Sets;



import java.util.Collections;

import java.util.Set;



/**

 * A {@link SideInputReader} representing a well-defined set of views, but not storing any values

 * for them. Used to check if a side input is present when the data itself comes from elsewhere.

 */

public class NullSideInputReader implements SideInputReader {



  private Set<PCollectionView<?>> views;



  public static NullSideInputReader empty() {

    return new NullSideInputReader(Collections.emptySet());

  }



  public static NullSideInputReader of(Iterable<? extends PCollectionView<?>> views) {

    return new NullSideInputReader(views);

  }



  private NullSideInputReader(Iterable<? extends PCollectionView<?>> views) {

    this.views = Sets.newHashSet(views);

  }



  @Override

  public <T> T get(PCollectionView<T> view, BoundedWindow window) {

    throw new IllegalArgumentException("cannot call NullSideInputReader.get()");

  }



  @Override

  public boolean isEmpty() {

    return views.isEmpty();

  }



  @Override

  public <T> boolean contains(PCollectionView<T> view) {

    return views.contains(view);

  }

}